1. Field of the Invention
The present invention relates to a display device and a driving method thereof, and in particular an organic light emitting device.
2. Description of the Related Art
Typically, an active matrix flat panel display includes a plurality of pixels for displaying images, and it displays images by controlling the luminance of each pixel according to given display information. Among the active matrix flat panel display devices, an organic light emitting display is a self-emissive display device having the advantages of low power consumption, a wide viewing angle, and a high response speed. Therefore, the organic light emitting display is being spotlighted as a next-generation display device to surpass the popularity of liquid crystal display (LCD).
Each pixel of an organic light emitting device includes a light-emitting device, a driving transistor, a switching transistor for applying a data voltage to the driving transistor, and a capacitor for storing the data voltage. The driving transistor outputs a current whose magnitude depends on the data voltage applied from the switching transistor. The light-emitting device emits light whose intensity is a function of the driving transistor's output current. Thereby, a space image is displayed.
Transistors are thin film transistors (TFT), which may be classified according to the type of active layer as either amorphous silicon or crystalline silicon thin film transistors, wherein such crystalline can be poly-crystalline or micro-crystalline.
When a black image is needed, a light-emitting device may still emit light if current leaks into the driving transistor. The darkness, or the contrast ratio in a black state, is determined by the magnitude of the leakage current. Particularly, when the driving transistor is a crystalline silicon thin film transistor, the leakage current is increased and the contrast ratio may be decreased, thus deteriorating display quality. This is more severe in OLEDs than in LCDs. This invention provides a device and a method for bypassing the leakage current in dark image display.
The above information disclosed in this BACKGROUND section is only for better understanding of the invention, therefore, it may contain information that does not form prior art.